Hildoceras bifrons

Hildoceras bifrons is an ammonoid that lived in the Early Jurassic Period, and became extinct about 175 million years ago.

H. bifrons is known as a ‘zone fossil’ - a fossil which has a precise distribution within layers of rock, and which can be used to identify layers of the same age.

The Hildoceras genus is named in honour of St. Hilda of Whitby (614-680 AD), whose feast day is celebrated on 17th November by the Roman Catholic Church.

Hildoceras ammonites are common along the Yorkshire coast, and are sometimes referred to as ‘snakestones’ due to ancient folklore that explained their origin as follows:

In the legend, St. Hilda was given the task of founding an Abbey on the plains of Whitby, but the area was infested with snakes. Snakes were seen as devilish and it was important to cast them out before creating a sacred building. St. Hilda prayed and after a short time the snakes coiled up and turned to stone, she then threw them off the cliff and that is why these creatures are found in the rocks around Whitby.

The absence of heads on the ammonite fossils is sometimes attributed to a further curse by St. Cuthbert.

In order to accentuate this belief, it was common in Victorian times, for fossil dealers to carve a snake’s head on ammonite fossils, in particular the species Hildoceras and Dactylioceras.